Justin Gatlin upset the odds to take a brilliant 100m gold in one of the greatest sprint races of all time.
The American ran 9.85 seconds to edge Portugal's Francis Obikwelu into second and reigning champion Maurice Greene into the bronze medal position.
Pre-race favourite Asafa Powell of Jamaica tied up and trailed home fifth as four men went under 9.90 seconds for the first time in history.
Gatlin said: "It hasn't sunk in. This is the most special moment of my life."
The 2003 World Indoors champion said he realised before the final that many had not considered him as a serious challenger for the gold medal.
"They were talking about Asafa and my team-mate Shawn Crawford," he added.
"Both were running against each other prior to the Games. I think that going out there and putting myself under pressure helped. I run well under pressure.
The 22-year-old said much of the race was a mental blur to him up until the final few metres.
"I don't remember much until the last moments of the race. I remember the gun going off and I knew in the last 10 metres I had to come home with power," he said.
"I've lived for this moment. It was a very great race, the
competition was stellar."
The Olympic champion revealed his preparations for the final were nearly scuppered by an intruder who entered the call room as he was putting his spikes on.
"He wanted a picture of the tattoos on my arms," said Gatlin.
"I was angry, I am not going to lie. This was the biggest race of my life and
I don't want anybody that I don't even know taking photos of me."
Greene, who was also deemed by many to be out of the running for the title, was content with his placing but also disappointed not to retain his Olympic crown.
He ran a season's best 9.87secs but was isolated in lane seven.
"I was just basically trying to pay attention to myself, not the others, but they got the better of me tonight," he said.
"My plan has not worked as well as I thought but I thank God for everything he has done for me."
Silver medallist Obikwelu, who set a new European record of 9.86 seconds, also had mixed feelings about his night's work.
"It was so close, I thought I had got it but it is not my day - but I thank God I am on the podium and in the first three," added the Portuguese sprinter.
Britain's Mark Lewis-Francis and Jason Gardener failed to make it through the semi-finals.
Lewis-Francis said: "I'm not heartbroken, but I'm gutted missing out on final by one spot."
Gardener said: "When I looked at the start list yesterday, I knew it was going to be very difficult.
"It's been a difficult summer and for me it's a big achievement making it to the Olympic